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ESS Wed Seminar: "Is There More Than One Methane Paradox? Cryptic Oxygen Control on Methane Production and Oxidation in Lakes" BY Professor Moritz Lehmann, University of Basel, Switzerland

Date and Time: 
March 14, 2018 -
12:30pm to 1:20pm
Y2E2, Room #111
Contact Email:
Contact Phone: 
(650) 724-4739
Event Sponsor: 
Department of Earth System Science

Lakes can be significant sources of methane (CH4) to the atmosphere. The standing paradigm is that CH4 production through methanogenesis occurs exclusively under anoxic conditions, and that at least in freshwater environments most of the biogenic CH4 is oxidized by aerobic methanotrophic bacteria under oxic conditions (“biological methane filter”). However, subsurface CH4 accumulation in oxic waters, a phenomenon known as the “methane paradox”, has been observed both in the ocean and in lakes. Analogously, methane-oxidizing bacteria may thrive also under micro-oxic conditions, i.e., they may be responsible for significant CH4 turnover at extremely low, or “hidden”, O2 concentrations. In this presentation, I will discuss the microbiological, geochemical, and physical controls on methane production and the efficiency of the biological CH4 filter in lakes. I will present hydrochemical, radio-label, stable isotope, and molecular data, which indicate methane production in oxic waters, and, referring to the “second methane paradox”, aerobic methane oxidation under seemingly anoxic conditions. I will also show experimental results that confirm nano-molar O2 requirements of aerobic methane oxidizers, and support a cryptic oxygen control on methane oxidation in the studied environments. The redox-boundaries traditionally accepted to separate CH4 production and consumption in lakes may not be that distinct after all.